The object of the proposed research project is to create improved noble metal Oxide pH electrodes by vacuum sputtering. Metal and reactive sputtering, used together, offer the investigators the means to create reproducible combinations of surface films so that accurate, fast and economical electrodes can be realized. As a direct result, miniature pH electrodes with low electrical resistance, which also respond rapidly to changes in pH may be directly used in biological fluids such as saliva, blood, plasma, spinal fluid and urine. The metal initially studied will be iridium because of prior work which has been done by this organization. Phase II of this work may offer two interesting areas of further investigation. The first would be the possible development of electrodes small enough to measure pH electrodes, i.e. enzyme-activated pH electrodes. These electrodes can indicate concentrations of glucose, urea, penicillin and other compounds of relevance to the health sciences.